Dry process photographic paper recording apparatus

ABSTRACT

Apparatus is provided for using a dry process photographic medium of the type described in Copending application Ser. No. 510,153 for recording data. The photographic medium includes an electrically conductive base which responds to electric power to produce developing heat internally. The apparatus of the invention includes electrodes in the form of rods, or rollers, for example, across which the medium is drawn, and electronic circuitry connected to the electrodes for introducing a controlled electric current flow through the base of the medium between the electrodes to develop latent images previously exposed on the medium, by the generation of electric power directly in the base.

June 3, 1975 DRY PROCESS PHOTOGRAPHIC PAPER RECORDING APPARATUS 3,826,896 7/l974 Thompson 2l9/388 Primary Examiner-C. L. Albritton Attorney, Agent, or Firm--Jessup & Beecher; Keith D.

ABSTRACT Apparatus is provided for using a dry process photographic medium of the type described in Copending application Ser. No. 510,153 for recording data. The photographic medium includes an electrically conductive base which responds to electric power to produce developing heat internally. The apparatus of the invention includes electrodes in the form of rods, or rollers, for example, across which the medium is drawn, and electronic circuitry connected to the electrodes for introducing a controlled electric current flow through the base of the medium between the electrodes to develop latent images previously exposed on the medium, by the generation of electric power directly in the base.

9 Claims, 2 Drawing Figures DEVELOPING IMAGES [75] Inventor: David Paul Gregg, Culver City,

Beecher [73] Assignee: Del Mar Engineering Laboratories,

Los Angeles, Calif. [22] Filed: Oct. 3, 1974 [21] Appl. No.: 511,791

{52] 0.8. CI. 219/216; 96/48 HD; 96/66 T [Sl] Int. Cl. H05h 1/00 [58] Field of Search 2l9/2l6, 388; 34/1; 354/298, 299; 96/48 HD, 66 T; 432/59, 227

[56] References Cited UNITED STATES PATENTS 2,503,779 4/[950 Story 34/] X 3,057,075 10/1962 Lippke 34/1 3,588.445 6/l97l Hopkins 2l9/2l6 X 3,640,l98 2/l972 James 96/45.2

IOB\ ENERGIZING soune: Light Emitting "o Diode405- M Voltage Multiplier E K4P-ref ANBENT TEMPERATURE C OLDER PAPER SPEED I l l l CONTROLLER coNrRoLLeH P DRY PROCESS PHOTOGRAPHIC PAPER RECORDING APPARATUS BACKGROUND OF THE INVENTION Copending application Ser. No. 510,153 discloses and claims a dry process photographic web which has an electrically conductive base and which is developed by internal heat generated in the base by electric power.

As explained in the Copending Application, dry process photographic film and paper are known and are commercially available which may be developed by the application of heat. The advantages of dry process photographic film and paper over the conventional wet process photographic medium are widely recognized, and the dry process film and paper are in present-day widespread use, particularly in data recording systems. In such systems, the dry process film or paper is exposed by a light source to produce latent images in the emulsion on the base. The exposed medium, in accor dance with the prior art practice, is then developed by the application of heat.

In order to develop the latent images on the exposed prior art dry process medium, the medium must be subjected to an elevated temperature over a substantial time interval. In the prior art recorders, the exposed dry process web is usually drawn over, or around, a heated platen, roller or drum, in order to raise the temperature of the exposed emulsion on the base to the required level. The heat from the platen, or other heated surface, must be conducted through the base itself to the emulsion so as to effectuate the development process. However, since the base has low thermal conduc tivity, successful development with the prior art dry process medium requires a heated surface of substantial size, and for the web to be drawn across the heated surface at a relatively low speed, in order that sufficient heat may be absorbed into the emulsion for a sufficient time to complete the development process.

Dry process papers and films have been recently produced in the prior art. These papers and films are composed of light sensitive materials which are developed solely by heating after conventional exposure. For example, the dry process silver papers and films generally have the same basic chemistry. The light sensitive component is silver halide in catalytic association with the image forming silver compound which is light insensitive. The emulsion must also contain the developing agent, and various developers can be used. Generally, a weak developer, such as a hindered phenol, is used. On exposure to light, or to an electron beam, a latent image of photolytic silver is formed on the base. The photolytic silver acts as a catalyst in forming the final silver image which is produced by a development pro cess, which involves raising the temperature of the emulsion to approximately 125C and maintaining that temperature over predetermined time intervals.

For continuous roll processing of exposed dry process paper or film, a heated drum is usually used in the prior art recorders to raise the emulsion temperature to the desired development level. However, continuous roll processing in the prior art is subject to certain limitations. For example, if the operation is intermittent, which is usually the case in a large number of applications, the base of the web resting against the heated surface tends to cook and spoil, so that any images exposed on such portions of the paper become obliterated. Also, the inclusion of a heated drum, or the like,

in the prior art chart recorder doubles its normal size.

Also, the geometry of the prior art recorders makes it necessary to space the exposing station a substantial distance from the drum, producing unused and wasted spaces in the medium between successive exposures. In addition, the thermal lag of the heated drum, or other element, as the speed at which the web moves is changed results in unacceptable waiting times until temperature stabilization is reached. The heat pro duced by the drum, or equivalent heated element, also tends to raise the temperature of the remaining photographic web stored in the recorder above acceptable levels, unless bulky, complex and expensive cooling means are incorporated into the equipment. All of the foregoing renders the cost of the prior art heat development recorders to a high level for most applications.

The aforesaid problems are solved in the apparatus of the present invention in that it provides for heat to be generated internally in dry process paper or film, such as described in the Copending Application, by the dissipation of electric power within an electrically conductive base, such as carbon-loaded paper. High thermal efficiency is realized, since the heat need not be conducted through a base of low thermal conductivity from an adjacent heat source, as is the case with the prior art recorders. Moreover, the apparatus, as will be described, permits the exposure station to be placed directly adjacent or even within the developing station.

The recorder of the present invention develops the dry process paper or film at a reduced development time, as compared with the prior art recorders, and it eliminates the need for bulky and expensive thermally inefficient external heat sources. As will become evident as the description proceeds, the apparatus of the present invention makes continuous development of dry process paper and film rolls practical, since only that portion of the web being developed is heated before passing on out of the recorder. Thus, intermittent operation of the recorder does not result in any portion of the web remaining in contact with a heated surface between operations, as is usually the case in the prior art recorders.

The recorder of the invention also results in decreasing the development time, as compared with the prior art recorders. Also, as noted above, the recorder of the present invention permits variable speed of the medium, since there is no thermal lag, as is the case when high temperature platens or drums are used, as in the prior art recorders. When it is desired to change speed of the medium, this can be carried out almost instanta neously since there is no appreciable thermal inertia in the web.

Paper sensitivity variations can be compensated in the apparatus of the present invention by means of a sensitometric closed loop control, as will be described. This leads to consistent image quality, and also to improved gray scale variations and high contrast.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of apparatus for recording data on a dry process photographic paper web, which incorporates the concepts of the present invention; and

FIG. 2 is a series of curves useful in explaining the operation of the apparatus of FIG. 1.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS The apparatus shown in FIG. 1 includes a dry process photographic web which may be of the type described in the Copending Application which includes an electrically conductive base. and which is developed by heat generated in its base by electric power generated by the passage of an electric current through the base. The medium 10 is drawn from the storage roll to the tensioning rollers over three longatcd electrodes 12. 13 and 14. These electrodes. for example. may be in the form of rods or rollers and. in the illustrated em bodiment. they are spaced and parallel with respect to one another.

An explosure station 16 is located at or between the electrodes 12 and 13. and the photographic medium 10 is exposed. for example. by means of a light beam 18 deflected and. perhaps. modulated by the indicia to be recorded on the medium 10. A first electronic circuit 20 is connected to the electrode 12. and it causes elec' tric current to flow through the electrically-conductivc base of the medium 10 between the electrode 12 and the electrode 13. the latter electrode being grounded. Since the heat generated within the medium 10 is pro portional to the electric power introduced to the por tion of the medium between the electrodes 12 and 13. the circuitry 20 serves to maintain the electric power essentially constant for any particular setting of the cir-- cuit controls. However. there is a different power level held constant depending upon changes in ambient temperature. web speed and sensitivity of the medium. and the different power levels with respect to ambient temperature and web speed are automatically controlled.

For this purpose. a series of controls. represented by potentiometers 30. 32 and 34 are interconnected with one another across a stable reference potential E The potentiometer is operated by an appropriate cow trollcr 36. the potentiometer 32 is operated by an appropriate controller 38, and the potentiometer 34 is manually set for the particular sensitivity of the inc dium to be used. The controller 36 is responsive to changes in ambient temperature to adjust the control 30 accordingly; the controller 38 is responsivc to changes in the speed of the medium 10 ato adjust the control 32 accordingly. Controllers such as the control lers 36 and 38 are known to the art. and. for that reason. there does not appear to be any necessity to de scribe the controllers in detail herein.

The potentiometers 30. 32 and 34 introduce a potential to a differential amplifier 42 which is proportional to the reference power (P required to flow through the medium 10 between the electrodes 12 and 13 to raise the emulsion on the medium 10 to the desired developing temperature. This potential is designated kqp The output of the differential amplifier 42 is applied to a power amplifier 46. so that the desired power level may be achieved. The output from the power amplifier 46 is passed through a resistor R, to the electrode 12.

The potential across the resistor R, is applied to a dil ferential amplifier 50 which produces an output prir portional to the current flow through the medium 10 between the electrodes 12 and 13. this output being designated tK i). The output from the ditTerential amplifier S0 is applied to a voltage multiplier 52. as is the potential of the electrode 12 (K el. The voltage multi- 4 plier produces an output (K 1 proportional to the actual power introduced to the medium 10 between the electrodes 12 and 13, and this output is applied to the differential amplifier 42.

The output value K p of the multiplier 52 may rise or fall during the operation of the system, causing the output of the differential amplifier 42 (K P K p) to rise and fall accordingly. so to maintain constant power in the medium 10 between the electrodes 12 and 13.

The two electrodes 12 and 13. and the circuitry 20 may be used alone to provide the desired developing temperature for the medium 10. In that case. the circuitry 20 is set. and the speed of the web 10 is adjusted. so that the portion of the medium between electrodes 12. 13 is heated to the developing temperature. and the medium experiences heat for sufficient time. so that the latent image on the medium 11) is fully developed as the medium is drawn off the electrode 13.

It is to be noted that the exposure station 16 may be located directly adjacent the electrode 12. so that minimum spacing is required between the exposure station and the development station. thereby to reduce wastage of the medium 10 between successive exposures to a minimum. as mentioned above.

As an alternative. the circuitry 20 and the speed of the web 10 may be set so that the medium is brought up to the emulsion developing temperature between the electrodes 12 and 13 in a minimum time. and is then held at that temperature by the heat developed in the medium between the electrodes 14 and 13 so as to complete the development process.

The power dissipated within the medium 10 between the electrodes 14 and 13 is provided. for example, by a power amplifier 100. A differential amplifier 102 is connected to the input of the power amplifier 100, and a controllable potential is applied to one input terminal of the differential amplifier 102 by means of a potentiometer 104 connected to the positive terminal of the stable reference potential E The actual development of the medium 10 can be controlled to a desired optical density level. by controlling the power dissipation within the medium between the electrodes 14 and 13 to the level required to produce the desired optical density. This is achieved. for example. by locating a light source. such as a light emitting diode 106 at the exposure station adjacent one edge of the medium 10. The light emitting diode 106 is energized from an appropriate energizing source 108, and its light intensity may be controlled by a potentiometer 110. The light intensity of the light emitting diode 166 is controlled. for example. so that the resulting line recorded by the diode. when developed. represents a reference optical density level.

The resulting line recorded by the diode 106 is detected. for example. by a detector unit 112 located between the electrodes 13 and 14. The detector unit 112 includes a light source. such as a light emitting diode 1 14, and light from the diode 114 is directed to a beam splitter 1 16 which may. for example. be a semitransparent reflector. The light emitting diode 114 is energized from a source 120, as controlled by a potentiometer The beam splitter 116 reflects one unit of the light from the diode 114 down on the surface of the line on the medium ll). Light reflected by the line passes through the beam splitter 116 with one half the light directed to an appropriate photocell 118. The potential output of the photocell, therefore, is continuously proportional to the optical density of the line resulting from the light source 106. The output from the photocell 118 is applied to the differential amplifier 102, and it serves to control the power introduced to the medium between the electrodes 14 and 13 to provide a developed optical density level which is thereby made to conform with the desired latent reference optical density produced by the light source 106.

For example, if the detector 112, while examining the optical density of the partially developed image of the line produced by the diode 106, predicts that the optical density of the line when it reaches the electrode 14, will not be the required optical density (for example, an optical density equal to 1.0), then it raises or lowers the output of the power amplifier proportionately, so that the reference optical density may be achieved.

The operation of the detector 112 and its associated circuitry is indicated by the curves of FIG. 2. These curves represent, for example, the history ofa point on the medium 10 as it passes from the exposure station to the developing station. In the curves, the temperature curve 1 illustrates a normal history, during which the power dissipated in the medium 10 is that re quired to raise to and maintain the emulsion at the proper developing temperature of, for example, 125C. The temperature curve 2 results when the optical density level of the partially developed reference line detected by the detector 112 is on the low side; and the temperature curve 3 results when the optical density level of the reference line is on the high side, These curves are given for descriptive purposes only, and are in no way intended to limit the concept of the invention.

The invention provides, therefore, an improved dry photographic medium recording apparatus which processes an electrically conductive photographic medium, and which, for example, includes appropriate controls to assure a proper optical density level in the developed medium.

While particular embodiments of the invention have been shown and described, modifications may be made, it is intended in the claims to cover the modifications which come within the true spirit and concept of the invention.

What is claimed is:

1. Apparatus for developing a dry process photographic web, said web comprising a base of electrically conductive material and a light sensitive photographic emulsion on the base formed of materials capable of being developed by heat, said apparatus including: electrode means across which the web is drawn, and

electrical circuit means connected to said electrode means for producing an electric power dissipation within the base of the web to cause internal developing heat to be generated thereby for the emulsion.

2. The apparatus defined in claim 1, in which said electrode means comprises first and second elongated electrically conductive elements spaced from one another, and in which said electrical circuit means is connected to said elements to produce an electric power dissipation within the portion of the web between the elements 3. The apparatus defined in claim 2, in which the elongated elements are in the form of rollers.

4. The apparatus defined in claim 1, in which said electrical circuit means includes regulating means for maintaining an essentially constant dissipation of said electric power within the base of the web for a particular speed of said web and for a particular ambient temperature.

5. The apparatus defined in claim 1, in which said electrical circuit means includes regulating means for changing the rate of dissipation of electric power in the base of the web for changes in web speed and for changes in ambient temperature.

6. The apparatus defined in claim 1, and which includes further electrode means spaced from said firstnamed electrode means, and further electrical circuit means connected to said further electrode means for producing an electric dissipation within a further portion of the base of the web to cause internal emulsiondeveloping heat to be generated in said further portion.

7. The apparatus defined in claim 2, in which said electrode means comprises a third electrically conductive element spaced from said first and second elements, and further electrical circuitry connected to said second and third elements for producing an electric power dissipation within the portion of the web be tween said second and third elements to cause internal emulsion-developing heat to be generated in said lastnamed portion of the web.

8. The apparatus defined in claim 7, and which in cludes optical density detecting means optically coupled to the portion of said web between said second and third elements, and control circuitry connecting said optical density detecting means into circuit with said further electrical circuitry to cause the development of said further portion of the web to reach a predetermined optical density.

9. The apparatus defined in claim 7, in which said first, second and third elements are in the form of rollers. 

1. Apparatus for developing a dry process photographic web, said web comprising a base of electrically conductive material and a light sensitive photographic emulsion on the base formed of materials capable of being developed by heat, said apparatus including: electrode means across which the web is drawn, and electrical circuit means connected to said electrode means for producing an electric power dissipation within the base of the web to cause internal developing heat to be generated thereby for the emulsion.
 1. Apparatus for developing a dry process photographic web, said web comprising a base of electrically conductive material and a light sensitive photographic emulsion on the base formed of materials capable of being developed by heat, said apparatus including: electrode means across which the web is drawn, and electrical circuit means connected to said electrode means for producing an electric power dissipation within the base of the web to cause internal developing heat to be generated thereby for the emulsion.
 2. The apparatus defined in claim 1, in which said electrode means comprises first and second elongated electrically conductive elements spaced from one another, and in which said electrical circuit means is connected to said elements to produce an electric power dissipation within the portion of the web between the elements.
 3. The apparatus defined in claim 2, in which the elongated elements are in the form of rollers.
 4. The apparatus defined in claim 1, in which said electrical circuit means includes regulating means for maintaining an essentially constant dissipation of said electric power within the base of the web for a particular speed of said web and for a particular ambient temperature.
 5. The apparatus defined in claim 1, in which said electrical circuit means includes regulating means for changing the rate of dissipation of electric power in the base of the web for changes in web speed and for changes in ambient temperature.
 6. The apparatus defined in claim 1, and which includes further electrode means spaced from said first-named electrode means, and further electrical circuit means connected to said further electrode means for producing an electric dissipation within a further portion of the base of the web to cause internal emulsion-developing heat to be generated in said further portion.
 7. The apparatus defined in claim 2, in which said electrode means comprises a third electrically conductive element spaced from said first and second elements, and further electrical circuitry connected to said second and third elements for producing an electric power dissipation within the portion of the web between said second and third elements to cause internal emulsion-developing heat to be generated in said last-named portion of the web.
 8. The apparatus defined in claim 7, and which includes optical density detecting means optically coupled to the portion of said web between said second and third elements, and control circuitry connecting said optical density detecting means into circuit with said further electrical circuitry to cause the Development of said further portion of the web to reach a predetermined optical density. 